German Offenlegungsschrift 3,536,820 describes a radio traffic service decoder which is set up to process digital signals. These signals are superimposed on an auxiliary carrier which is broadcast over radio transmitters together with the FM radio program. The information contained in these digital signals can consequently be transmitted without interference parallel to the actual radio program. This also applies in particular to traffic news, which can be decoded by demodulation of the aforesaid auxiliary carrier.
If the traffic news transmitted as digital signals is drafted according to the same formation principles as the traffic news broadcast in ordinary language, then it is also possible to transmit, instead of the complete information, memory addresses which call up standardized text stored in memories at the receiving end. As a consequence, it is possible to make do with a substantially smaller data capacity during the transmission. The consequence of this is that it is now possible for considerably more traffic news to be transmitted on individual events than has hitherto been the case.
While maintaining the selection criterion hitherto used for the traffic news, which is essentially oriented to the number of drivers affected, it would be possible, also with cyclical repetition, to transmit supra-regional traffic news relating to the territory of the Federal Republic of Germany, and if appropriate the neighboring countries, over all the UHF station chains. Another possibility is to limit the region to which the traffic news relates, for instance to the catchment or reception area of the station or the station chain, but then to extend the selection of traffic news also to those events which affect only a few drivers.
Regardless of the selection of transmitted traffic news made, the volume of news would overtax the attention of the driver if all the news was presented to him optically or acoustically.
It is has already been proposed that a selection be made from the traffic news displayed or represented. This can be carried out on the basis, for example, of the planned journey route which the driver has entered via an input device as data on the route to be travelled. It is then ensured that only the traffic news relating to this journey route appears on the output device.
However, the limitation to the journey route commenced can be too narrow if the driver is also interested in the traffic situation of other places or long-term situations affecting the traffic there, since he may wish to drive to these places at short notice.
If the driver is in a border area or transitional area of stations or station chains which transmit only regionally limited traffic news, then it is possible that a station is being received which, although it transmits traffic news, does not cover the region currently of interest.